diff --git a/SpanshRouter/PlaceHolderEntry.py b/SpanshRouter/PlaceHolderEntry.py
index fb58798..8fd1bc3 100644
--- a/SpanshRouter/PlaceHolderEntry.py
+++ b/SpanshRouter/PlaceHolderEntry.py
@@ -6,4 +6,5 @@ from PlaceHolder import PlaceHolder
 class PlaceHolderEntry(Entry, PlaceHolder):
     def __init__(self, parent, placeholder, **kw):
         Entry.__init__(self, parent, **kw)
+        self.var = self["textvariable"] = StringVar()
         PlaceHolder.__init__(self, placeholder)
\ No newline at end of file
diff --git a/SpanshRouter/SpanshRouter.py b/SpanshRouter/SpanshRouter.py
index 7285f74..ccd3b50 100755
--- a/SpanshRouter/SpanshRouter.py
+++ b/SpanshRouter/SpanshRouter.py
@@ -91,6 +91,9 @@ class SpanshRouter():
         self.error_lbl.grid_remove()
         row += 1
 
+        # Check if we're having a valid range on the fly
+        self.range_entry.var.trace('w', self.check_range)
+
         self.show_plot_gui(False)
 
         if not self.route.__len__() > 0:
@@ -420,6 +423,17 @@ class SpanshRouter():
             except:
                 print("No route to delete")
 
+    def check_range(self, name, index, mode):
+        value = self.range_entry.var.get()
+        if value.__len__() > 0 and value != self.range_entry.placeholder:
+            try:
+                float(value)
+                self.range_entry['fg'] = self.range_entry.default_fg_color
+                self.hide_error()
+            except ValueError:
+                self.show_error("Invalid range")
+                self.range_entry['fg'] = "red"
+
     def cleanup_old_version(self):
         try:
             if (os.path.exists(os.path.join(self.plugin_dir, "AutoCompleter.py"))